Neospora is a newly recognized Toxoplasma-like parasite and a major cause of abortion/congenital disease in dairy cattle. In an earlier study, we successfully produced experimental transplacental Neospora fetal infection in nonhuman primates. The resulting fetal infections resembled human fetal toxoplasmosis. In that study, dams were inoculated at gestational day 45 (GD 45) and fetuses were removed surgically at GD 113. In the present study, 6 pregnant macaques were divided into 2 groups, inoculated with Neospora tachyziotes at either GD 25 or GD 45. Pregnant control monkeys were given uninfected inocula. In all but one instance (a single dam in the GD 25 group), the cell culture inocula given to the pregnant monkeys was later found to be contaminated with Bovine Virus Diarrhea Virus (BVDV). This BVDV contaminant had a marked deleterious effect on in vivo Neospora parasite behavior resulting in failure of transplacental Neospora infections in 4/6 infected dams. The single fetus from the GD 25 dam receiving no contaminating BVDV died 50 days PID with severe encephalitis and disseminated Neospora infection. One additional dam in the GD 45 group gave birth to a normal-appearing offspring subsequently found to have chronic resolved Neospora encephalitis with mild unilateral hydrocephalus ex vacuo. Review of cell culture records and results of a concurrent bovine fetal study point to BVDV contamination as the cause for negative results in the remaining Neospora infected monkeys. Results from the 2 successful transplacental infections in this study suggest that early gestational infection (GD 25) leads to fetal death, while fetal infection during development of fetal immunity (GD 45) may result in viable offspring with congenital encephalitis and hydrocephalus. BVDV cell culture contamination has been eliminated and we are currently repeating this study to verify these conclusions. *KEY* Toxoplasma, Fetus encephalitis, Hydrocephalus